Introduces PgBouncer as a connection pooler between the API service and
PostgreSQL in docker-compose.prod.yml, reducing connection overhead and
improving concurrency under production load.
- Add PgBouncer service (edoburu/pgbouncer:1.23.1-p2) with transaction
pool mode, max_client_conn=200, default_pool_size=20
- Route API DATABASE_URL through PgBouncer (port 6432), keep direct
connection (DATABASE_URL_DIRECT) for Prisma migrations/introspection
- Create infra/pgbouncer/ config: pgbouncer.ini, userlist template,
and entrypoint script with runtime env-var substitution
- Update prisma.config.ts to prefer DATABASE_URL_DIRECT for migrations
- Add K6 load test (e2e/load/pgbouncer-pool-test.js) with ramp-up to
200 VUs, pool exhaustion detection, and p95 < 2s threshold
- Add PgBouncer env vars to .env.example
Co-Authored-By: Paperclip <noreply@paperclip.ing>